1. Field of the Invention
The present invention generally relates to devices that capture audio and video. In particular, the present invention relates to audio/video (A/V) capture devices that include a video zoom feature.
2. Background
Devices exist that allow a user to capture and record audio and video. Such audio/video (A/V) capture devices include, for example, digital and analog camcorders as well as selected models of digital cameras, cellular telephones and media players. Certain A/V capture devices may also allow a user to capture audio and video for transmission to one or more other devices via a suitable transmission medium.
Conventional A/V capture devices typically include a video acquisition section for capturing video and an audio acquisition section for capturing audio. The video acquisition section may include a zoom lens. A zoom lens comprises a mechanical assembly of lens elements configured such that the focal length of the lens can be varied. Increasing the focal length of the zoom lens increases the magnification of the video image while simultaneously reducing the field of view. Reducing the focal length of the zoom lens reduces the magnification of the video image while simultaneously increasing the field of view. The ability to adjust the focal length of a zoom lens of an A/V capture device in this manner is referred to herein as “video zoom.” Increasing the focal length of the zoom lens may also be referred to herein as increasing the level or amount of video zoom while reducing the focal length of the zoom lens may also be referred to herein as reducing the level or amount of video zoom. Video zoom is generally considered a desirable feature because, among other things, it allows a user to capture detailed video of subject matter that is relatively far away from the A/V capture device.
Recently, a distinction has been made between “optical” video zoom and “digital” video zoom. Optical video zoom refers to the adjustment of the focal length of a zoom lens to change the level of magnification and the field of view of the video image as previously described. In contrast, “digital” video zoom does not truly change the level of magnification or the field of view of the video image but instead simulates optical video zoom by enlarging pixels in a portion of a video image and by optionally using an interpolation technique to fill in gaps between the enlarged pixels. As used herein, the term “video zoom” may be used to refer to both optical and digital video zoom. In the context of digital video zoom, increasing the amount of video zoom refers to increasing the amount of enlargement to be applied to a portion of the video image while reducing the amount of video zoom refers to reducing the amount of enlargement to be applied to a portion of the video image.
The audio and video streams captured by conventional A/V capture devices are typically not spatially synchronized. That is to say, assuming that the spatial locations of an A/V capture device and the audio sources that surround it are unchanging, the audio acquisition section of the A/V capture device will generally capture the same level of audio from the same audio sources regardless of whether those audio sources are within the field of view of the video acquisition portion of the A/V capture device. This lack of spatial synchronization may become evident, for example, when a user of an A/V capture device increases the amount of video zoom to obtain a close-up view of a particular object or person. Although certain audio sources may fall outside the field of view of the video image as a result of the increased video zoom, the audio acquisition section of the A/V capture device will continue to capture audio from sources that lie outside the field of view. This can result in the inclusion of undesired audio in the captured A/V stream and lead to confusion about what an audio source might be when the A/V stream is subsequently played back to a user.